Isolating Sweet Corn

Seed-catalog descriptions of ultrasweet and tender kernels might tempt a gardener to plant several of the new hybrid corn—and throw in a few rows of popcorn and ornamental corn for good measure.

Big mistake. Corn is wind-pollinated, and pollen from the tassels of one variety can drift to the silks of another. When different types of corn cross-pollinate, the taste and tenderness of the resulting kernels are affected. The worst-case scenario: inedible ears.

Advances in corn breeding over the past few decades have led to new classes of hybrids, including supersweet, synergistic, and sugar-enhanced. In addition to their unusually sweet flavor, these hybrids stay sweet longer after harvest—a distinct advantage for market farmers. While many gardeners have switched over to the sweeter hybrids, some still prefer the old-fashioned taste of traditional varieties of sweetcorn, such as ‘Silver Queen’ and ‘Golden Bantam’.

The genes that are responsible for sweetness result not from genetic engineering but from natural mutations in field corn. Through controlled crosses, plant breeders create hybrid varieties in which the sugar-producing genes take the place of starch-producing genes. But the wrong kind of pollen can negate the breeder’s work by reintroducing genes that lead to tough, starchy kernels.

To avoid stray pollen and preserve sweetness, all types of sweet corn must be isolated from field corn, ornamental corn, and popcorn. Additionally:

Traditional: Isolate from the pollen of supersweet varieties.

Sugar enhanced: Isolate from traditional and supersweet pollen.

Synergistic: Isolate from traditional and supersweet pollen.

Supersweet: Isolate from all other types of corn.

Physical isolation requires a separation of at least 100 feet between plantings and may be impossible in a small home garden. (Even at 100 feet apart, stray pollen may drift in, causing a few starchy kernels per ear.) A more practical way for home gardeners to prevent cross-pollination is by staggering planting times or by selecting varieties with different numbers of days to maturity, so that the varieties will not be releasing pollen simultaneously. Aim for a separation of 14 days between maturation dates.

Photograph by Christa Neu

Originally published in Organic Gardening magazine, February/March 2014